unround
1 of 2verb
un·round ˌən-ˈrau̇nd 
unrounded; unrounding; unrounds
transitive verb
1
: to pronounce (a sound) without lip rounding or with decreased lip rounding
2
: to spread (the lips) laterally
necessary to unround the lips in pronouncing \\ē\\
unround
2 of 2adjective
: pronounced with the lips not rounded
Word History
First Known Use
Verb
1874, in the meaning defined at sense 1
Adjective
1958, in the meaning defined above